Impact of a Hybrid Energy Storage Module on Power Quality of a Fossil Fuel Generator

As the Navy's demands for high power transient loads aboard an all-electric fleet evolve, so too does the need for alternative energy sources to backup the more traditional forms of power generation. Such applications in need of support include electrical grid backup and directed energy weapon systems such as electromagnetic launchers (EMLs), laser systems, and high power microwave (HPM) generators, among others. Among the alternative sources receiving considerable attention are energy storage devices such as rechargeable electrochemical batteries and capacitors. In the applications mentioned above, these energy storage devices offer the ability to serve a dual role as both a power source to the various loads and as high power loads themselves to the fossil fuel generation when the high power transient loads are in periods of downtime. Recent developments in electrochemical energy storage have made lithium-ion batteries (LIBs) seem like the obvious choice. Previous research has shown that while LIBs offer high power density, operation at C rates in excess of 5C can be detrimental to both the safety and operational life span of the device. In order to preserve the batteries, it is best to limit their rate of operation. It is therefore proposed that high energy density LIBs be combined, through the use of actively controlled power electronics, with high power density electric double layer capacitors (EDLCs) so that an energy storage device that offers both high energy and high power can be utilized and operated in the most reliable, safe, and efficient manner possible. Such a configuration is typically known in the field as a hybrid energy storage module (HESM). During generator start up or down time, the combined high energy density and high power density of the HESM provides the capability to source high power loads for an extended period of time at the high rates they demand. When the generator is operational, the HESM has the ability to act as a high-energy reservoir to harvest energy from the generator while the loads are in short periods of inactivity. This enables the generator to be continuously base loaded, thereby maintaining a high level of efficiency at all times while theoretically maintaining the required power quality of the AC bus. At UT Arlington (UTA), an actively controlled HESM has been constructed and evaluated under the operational scenarios discussed above[1]. The experimental setup and results obtained thus far will be presented here.